Quantum turbulence of bellows-driven<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mn>4</mml:mn></mml:msup></mml:math>He superflow: Steady state

Babuin, Simone; Stammeier, Mathias; Varga, E.; Rotter, M.; Skrbek, L.

doi:10.1103/physrevb.86.134515

Cited by 54 publications

(50 citation statements)

References 81 publications

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“…Second-sound attenuation is the most powerful (and historically the oldest) (7) measurement tool in 4 He, revealing the vortex-line density L-the total length of the quantized vortex line in a unit volume (23). Because second sound is an antiphase oscillation of normal and superfluid components, this technique cannot be used below 1 K (because there is little normal fluid) or in 3 He at any temperature (second-sound waves are overdamped by the large viscosity of the normal fluid).…”

Section: Experimental Methods For Quantum Turbulencementioning

confidence: 99%

Introduction to quantum turbulence

Barenghi

Skrbek

Sreenivasan

2014

Proc. Natl. Acad. Sci. U.S.A.

284

264

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The term quantum turbulence denotes the turbulent motion of quantum fluids, systems such as superfluid helium and atomic Bose-Einstein condensates, which are characterized by quantized vorticity, superfluidity, and, at finite temperatures, two-fluid behavior. This article introduces their basic properties, describes types and regimes of turbulence that have been observed, and highlights similarities and differences between quantum turbulence and classical turbulence in ordinary fluids. Our aim is also to link together the articles of this special issue and to provide a perspective of the future development of a subject that contains aspects of fluid mechanics, atomic physics, condensed matter, and low-temperature physics.Turbulence is a spatially and temporally complex state of fluid motion. Five centuries ago, Leonardo da Vinci noticed that water falling into a pond creates eddies of motion. Today, turbulence still provides physicists, applied mathematicians, and engineers with a continuing challenge. Leonardo realized that the motion of water shapes the landscape. Today's researchers appreciate that many physical processes, from the generation of the Galactic magnetic field to the efficiency of jet engines, depend on turbulence.The articles in this collection are devoted to a special form of turbulence known as quantum turbulence (1-3), which appears in quantum fluids. Quantum fluids differ from ordinary fluids in three respects: (i) they exhibit two-fluid behavior at nonzero temperature or in the presence of impurities, (ii) they can flow freely, without the dissipative effect of viscous forces, and (iii) their local rotation is constrained to discrete vortex lines of known strength (unlike the eddies in ordinary fluids, which are continuous and can have arbitrary size, shape, and strength). Superfluidity and quantized vorticity are extraordinary manifestations of quantum mechanics at macroscopiclength scales.Recent experiments have highlighted quantitative connections, as well as fundamental differences, between turbulence in quantum fluids and turbulence in ordinary fluids (classical turbulence). The relation between the two forms of turbulence is indeed a common theme in the articles collected here. Because different scientific communities (lowtemperature physics, condensed-matter physics, fluid dynamics, and atomic physics) have contributed to progress in quantum turbulence, † the aim of this article is to introduce the main ideas in a coherent way. Quantum FluidsIn this series of articles, we shall be concerned almost exclusively with superfluid 4 He, the B-phase of superfluid 3 He, and, to a lesser extent, with ultracold atomic gases. These systems exist as fluids at temperatures on the order of a Kelvin, milliKelvin, and microKelvin, respectively.‡ Their constituents are either bosons (such as 4 He atoms with zero spin) or fermions (such as 3 He atoms with spin 1/2). This difference is fundamental: the former obey Bose-Einstein statistics and the latter Fermi-Dirac quantum statistics.Let us consider an...

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Section: Experimental Methods For Quantum Turbulencementioning

confidence: 99%

Introduction to quantum turbulence

Barenghi

Skrbek

Sreenivasan

2014

Proc. Natl. Acad. Sci. U.S.A.

284

264

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“…[2,6,22,25,35,36] and other superfluid transitions reported in pipes, channels, and flows through apertures with various types of thermomechanical forcing; e.g., see Refs. [37][38][39][40][41] and references therein. In Subsec.…”

Section: A Critical Velocities In Superfluid Counterflowsmentioning

confidence: 99%

Disproportionate entrance length in superfluid flows and the puzzle of counterflow instabilities

2017

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Systematic simulations of the two-fluid model of superfluid helium (He-II) encompassing the Hall-Vinen-Bekharevich-Khalatnikov (HVBK) mutual coupling have been performed in two-dimensional pipe counterflows between 1.3 and 1.96 K. The numerical scheme relies on the lattice Boltzmann method. A Boussinesq-like hypothesis is introduced to omit temperature variations along the pipe. In return, the thermomechanical forcings of the normal and superfuid components are fueled by a pressure term related to their mass-density variations under an approximation of weak compressibility. This modeling framework reproduces the essential features of a thermally driven counterflow. A generalized definition of the entrance length is introduced to suitably compare entry effects (of different nature) at opposite ends of the pipe. This definition is related to the excess of pressure loss with respect to the developed Poiseuille-flow solution. At the heated end of the pipe, it is found that the entrance length for the normal fluid follows a classical law and increases linearly with the Reynolds number. At the cooled end, the entrance length for the superfluid is enhanced as compared to the normal fluid by up to one order of magnitude. At this end, the normal fluid flows into the cooling bath of He-II and produces large-scale superfluid vortical motions in the bath that partly re-enter the pipe along its sidewalls before being damped by mutual friction. In the superfluid entry region, the resulting frictional coupling in the superfluid boundary layer distorts the velocity profiles toward tail flattening for the normal fluid and tail raising for the superfluid. Eventually, a simple analytical model of entry effects allows us to re-examine the long-debated thresholds of T 1 and T 2 instabilities in superfluid counterflows. Inconsistencies in the T 1 thresholds reported since the 1960s disappear if an aspect-ratio criterion based on our modeling is used to discard data sets with the strongest entry effects. Furthermore, it is observed that entry effects can spuriously reproduce the signature of a T 2 transition with a normal flow remaining laminar.

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“…1). For second-sound sensors, standard design of capacitively actuated gold-plated Nuclepore membrane is used [5] and thermometry is accomplished using commercial Ge-on-GaAs film resistors. Using this system we are able to monitor initial local VLD build-up.…”

Section: Methodsmentioning

confidence: 99%

Transition to Quantum Turbulence and Streamwise Inhomogeneity of Vortex Tangle in Thermal Counterflow

Varga¹,

Babuin²,

L'vov³

et al. 2016

J Low Temp Phys

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We report preliminary results of the complementary experimental and numerical studies on spatiotemporal tangle development and streamwise vortex line density (VLD) distribution in counterflowing 4 He. The experiment is set up in a long square channel with VLD and local temperature measured in three streamwise locations. In the steady state we observe nearly streamwisehomogeneous VLD. Experimental second sound data as well as numerical data (vortex filament method in a long planar channel starting with seeding vortices localized in multiple locations) show that the initial build up pattern of VLD displays complex features depending on the position in the channel, but the some tangle properties appear uniform along its length.

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Quantum turbulence of bellows-driven4He superflow: Steady state

Cited by 54 publications

References 81 publications

Introduction to quantum turbulence

Introduction to quantum turbulence

Disproportionate entrance length in superfluid flows and the puzzle of counterflow instabilities

Transition to Quantum Turbulence and Streamwise Inhomogeneity of Vortex Tangle in Thermal Counterflow

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